Help needed with misfire when radiator fans are at high speed
07-30-2022, 07:55 AM
#61
Rennlist Member
I'm not ignoring the questions you asked above. I'll answer your questions from memory because I'm not actively working on the car tonight, and I won't be again until I get home.
1. No, I haven't had the alternator tested, and I don't have an alternate to swap in.
2. The voltage at the cable connection on the alternator just after starting was ~14V. Same at the positive terminal of the battery. Neither changed more than 0.2V between running warm and running cold, even with no accessories. With all accessories, it drops to about 12.5V.
3. I don't know the alternator manufacturer off-hand. I have no reason to believe it's not the stock Bosch unit.
a. Yes, it's two wires.
b. Yes, I think the alternator light illuminates when the engine is off. I haven't looked too closely at that since I first got past the various no-start condition tests when I got the car.
c. I added the variable voltage regulator to see if that would help the alternator keep the voltage higher, and it did. Prior to that, it would hop around between 10V and 12V (and it still ran smoother than it does now).
d. The variable voltage regulator was the same cost as a new set of bushes for the Bosch, and it came with new bushes to boot.
And I haven't ruled out the alternator. I just think it's still also possibly the ECU. I'm not eliminating that option until I've tested the voltage at that circuit when the fuel pressure drop is happening. That's an easy/free test, and I have a new in-tank filter to replace while I'm in there anyway.
If the alternator were easier to bench test or swap out, I would probably have already done that. I am trying to prevent buying things (so far) that don't already need to be replaced for other reasons. I know that it does seem to keep the voltage high enough to run, never dropping below 12.5V even with everything on. And when I drop it that low with the adjustable voltage regulator, the engine still runs smoothly. Even you said you agreed with that in your post here after being sure the alternator was the culprit beforehand: https://rennlist.com/forums/924-931-...l#post18188178
To be extra clear, this misfiring is not only happening when the alternator is warm or when driving on warm days.
-N
1. No, I haven't had the alternator tested, and I don't have an alternate to swap in.
2. The voltage at the cable connection on the alternator just after starting was ~14V. Same at the positive terminal of the battery. Neither changed more than 0.2V between running warm and running cold, even with no accessories. With all accessories, it drops to about 12.5V.
3. I don't know the alternator manufacturer off-hand. I have no reason to believe it's not the stock Bosch unit.
a. Yes, it's two wires.
b. Yes, I think the alternator light illuminates when the engine is off. I haven't looked too closely at that since I first got past the various no-start condition tests when I got the car.
c. I added the variable voltage regulator to see if that would help the alternator keep the voltage higher, and it did. Prior to that, it would hop around between 10V and 12V (and it still ran smoother than it does now).
d. The variable voltage regulator was the same cost as a new set of bushes for the Bosch, and it came with new bushes to boot.
And I haven't ruled out the alternator. I just think it's still also possibly the ECU. I'm not eliminating that option until I've tested the voltage at that circuit when the fuel pressure drop is happening. That's an easy/free test, and I have a new in-tank filter to replace while I'm in there anyway.
If the alternator were easier to bench test or swap out, I would probably have already done that. I am trying to prevent buying things (so far) that don't already need to be replaced for other reasons. I know that it does seem to keep the voltage high enough to run, never dropping below 12.5V even with everything on. And when I drop it that low with the adjustable voltage regulator, the engine still runs smoothly. Even you said you agreed with that in your post here after being sure the alternator was the culprit beforehand: https://rennlist.com/forums/924-931-...l#post18188178
To be extra clear, this misfiring is not only happening when the alternator is warm or when driving on warm days.
-N
I appreciate your clarification and your situation stumps me.
From your description, 12.5 volts at the battery terminal with fans operating should be sufficient voltage to operate the fuel pump at it's rated pressure output.
Just as a side note,
The fuel pressure dropping from P1 of 40 to P2 of 20 affects the fuel flow rate at the fuel injector to 0.707 x normal flow rate. The change of flow rate varies as the square root of ( P2/P1).
There is a gremlin some where and needs to be exposed.
As a test, run a bypass 14 gage wire directly from the positive terminal of the battery to the positive terminal of the fuel pump. This eliminates all the ancillary relays, positive supply voltage to ECU, etc. If you want to be safe, install an inline 20 amp fuse in case something shorts out, could also add a toggle on/off switch if you want. See what is the outcome is on the voltage at the fuel pump and fuel pressure on the rail without bypass, normal operation vs same readings with the bypass.
Last edited by T&T Racing; 07-30-2022 at 08:00 AM.
08-08-2022, 08:57 PM
#63
Rennlist Member
Thread Starter
I think I've found it. I still need to test drive to be sure, but this seems pretty cut and dry to me. Here's the voltage I was seeing at the fuel pump while the misfiring was coming every few seconds:
And then, I swapped out my Focus 9 Technologies solid state fuel relay for a mechanical one I repaired:
Night and day difference. Zero stuttering with the mechanical relay, solid 12V to the fuel pump, even with all the accessories on.
-N
-N
Last edited by neilschelly; 08-09-2022 at 06:42 AM.
08-09-2022, 06:43 AM
#65
Rennlist Member
Thread Starter
-N
08-09-2022, 10:02 AM
#67
Rennlist Member
Thread Starter
08-09-2022, 10:19 AM
#68
Addict
Rennlist Member
Rennlist Member
Is it possible for it to have gotten damaged in some way, like maybe an over-voltage condition? Would be interesting to disassemble it and look for burnt components.
08-09-2022, 10:30 AM
#69
Rennlist Member
Thread Starter
-Neil
08-09-2022, 07:26 PM
#70
Rennlist Member
Thread Starter
Last night, after posting, I went for a drive, about 10 miles, engine loaded, high and low rpms, every accessory on, etc. No misfires. During all of these issues, I've only once had issues starting the car when in the pouring rain that one time.
This morning and evening, the car cranks and has plenty of fuel pressure, but it won't start. I tried both relays, but since there is fuel pressure, I doubt that would make a difference. I did get a tiny stutter once, but otherwise, I couldn't get it to run. At all.
This seems like an entirely different issue now, but I had one good drive last night! WTF...
-N
Related note: F9 was super responsive, and they are sending me a new relay.
This morning and evening, the car cranks and has plenty of fuel pressure, but it won't start. I tried both relays, but since there is fuel pressure, I doubt that would make a difference. I did get a tiny stutter once, but otherwise, I couldn't get it to run. At all.
This seems like an entirely different issue now, but I had one good drive last night! WTF...
-N
Related note: F9 was super responsive, and they are sending me a new relay.
08-10-2022, 10:37 AM
#71
Addict
Rennlist Member
Rennlist Member
I contacted F9 to see what they want to do first. They have a 4-year warranty. If they want to inspect it, great.If not, I'll gladly pop it open and see what I can find. Personally, I'm looking forward to upgrading to the newer/nicer relay from them with the diagnostic LEDs. If I'd have seen them misbehaving earlier, I'll bet this problem would have been resolved sooner.
-Neil
-Neil
Last edited by austin944; 08-10-2022 at 10:50 AM.
08-10-2022, 06:18 PM
#72
Rennlist Member
Last night, after posting, I went for a drive, about 10 miles, engine loaded, high and low rpms, every accessory on, etc. No misfires. During all of these issues, I've only once had issues starting the car when in the pouring rain that one time.
This morning and evening, the car cranks and has plenty of fuel pressure, but it won't start. I tried both relays, but since there is fuel pressure, I doubt that would make a difference. I did get a tiny stutter once, but otherwise, I couldn't get it to run. At all.
This seems like an entirely different issue now, but I had one good drive last night! WTF...
-N
Related note: F9 was super responsive, and they are sending me a new relay.
This morning and evening, the car cranks and has plenty of fuel pressure, but it won't start. I tried both relays, but since there is fuel pressure, I doubt that would make a difference. I did get a tiny stutter once, but otherwise, I couldn't get it to run. At all.
This seems like an entirely different issue now, but I had one good drive last night! WTF...
-N
Related note: F9 was super responsive, and they are sending me a new relay.
08-10-2022, 08:37 PM
#73
Rennlist Member
Thread Starter
There was no spark at all. I swapped out the brand new MSD ignition coil for the old stock one. That was among the parts I replaced, but didn't technically need to. The stock one just looked bad, and I liked the idea of having all new components in the ignition system (and couldn't find a stock replacement).
Started right up like it never wondered if it should as soon as the stock coil was hooked up again. I cannot fathom what could have caused a total failure of that so soon. I will definitely have to have a look around the electrical system to see if I can find anything else misbehaving. I certainly haven't seen any evidence of it yet.
-Neil
Started right up like it never wondered if it should as soon as the stock coil was hooked up again. I cannot fathom what could have caused a total failure of that so soon. I will definitely have to have a look around the electrical system to see if I can find anything else misbehaving. I certainly haven't seen any evidence of it yet.
-Neil
08-11-2022, 10:28 AM
#74
Burning Brakes
Join Date: Oct 2021
Location: Southern WI - 89S2 Megasquirt PNP
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Joe at Focus9 just replaced an old solid state relay that burnt out on me free of charge, no questions asked. Hes a great guy and stands by his work.
It was clearly well outside of the 4 year warranty range, but he still replaced it.
It was clearly well outside of the 4 year warranty range, but he still replaced it.
Last edited by walfreyydo; 08-11-2022 at 10:33 AM.
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